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Tweaking TT .40 for max performance?

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Tweaking TT .40 for max performance?

Old 09-14-2003, 04:47 PM
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idranoel
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Default Tweaking TT .40 for max performance?

I have broken in a TT.40 for my Predator using the chopped prop method (it was kind of scary). Anyway, the engine runs GREAT and now I just have a few questions. First, should I take the baffle out of the muffler? Second, when should I take the shim out? Third, right now I am getting about 16,350 rpm out of it on 10% Wildcat and the standard APC 9x6 prop. Does that sound OK? I haven't tried to wring every last bit out. (I've only put about 6 tanks through it.) Any other tips would be appreciated. Thanks in advance!

Dan
Old 09-14-2003, 05:34 PM
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Ed Smith
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Default RE: Tweaking TT .40 for max performance?

What is the intended use for this engine? Will it be used in a specific racing event?

Ed S.
Old 09-14-2003, 07:42 PM
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idranoel
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Default RE: Tweaking TT .40 for max performance?

Sorry for not specifying what kind of racing. (I didn't think it would matter and I only know of one kind of racing that involves Predators and TT.40s). Although I have never competed, I am new to the world of pylon racing and would be starting in AMA 424 (Sport Quickie). Thanks,

Dan
Old 09-15-2003, 06:55 AM
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luv to race
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Default RE: Tweaking TT .40 for max performance?

First... In AMA 424 I think the rules say "Box Stock" concerning the engine. So, no you cannot remove the baffle out of the muffler. Second, the 424 class has a max RPM limit of 16,500.... So if the CD does his/her job and runs all the motors in the morning and throughout the day, you'll get caught...

But. I like your enthusiasm..
Old 09-15-2003, 07:08 AM
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Ed Smith
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Default RE: Tweaking TT .40 for max performance?

Compliance to racing rules is why I asked the question.

If as you say you have never competed or raced in a Pylon Race I would suggest you concentrate more on flying a tight constitent course than on trying to squeeze an extra 200 rpm from your engine.

Ed S.

PS I see the author of the previous post is from "Liquored" in FL. Is there really a place called that. Maybe I should move!!
Old 09-15-2003, 09:52 AM
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DMyer
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Default RE: Tweaking TT .40 for max performance?

Ditto what Ed Smith said... practice practice practice... As for your engine... sounds like it is already plenty good and will get even better as it runs in more. My advice for your engine is to replace the rear bearing so that you will be able to get that practice. The TT40 Pro rear bearing has a nasty record of coming apart ruining the engine. Dave Shadel at Performace Specialties can fix you up for $15. Also... remove the internal spring from the throttle barrel and locktite the barrel set screw on... When the barrel falls out(it will)... the spring sometimes gets swallowed... not good. I also disassembled my muffler and JB-Welded it together real good to keep it intact when the muffler bolt breaks(it will). When the bolt breaks, get some 6-32 all-thread from McMaster Carr, drill out the holes on each end and secure with lock-nuts. None of these things change the performance one bit... but they will enhance reliability greatly which is what you need to practice a lot. Good luck and good flying!

Dan
Old 10-14-2003, 07:00 PM
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rsieminski
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Default RE: Tweaking TT .40 for max performance?

I have broken in a TT.40 for my Predator using the chopped prop method
What is this method? What is it supposed to accomplish?
Thanks,
--Rick
Old 10-15-2003, 05:54 AM
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Ed Smith
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Default RE: Tweaking TT .40 for max performance?

You have probably heard of the club"Expert's" method of engine break in. Run it slobbering rich for three gallons. The one person to avoid in a club is the engine expert.

An ABC type engine has no piston ring and relies on a tight fit at TDC for the piston/sleeve seal. If the piston/sleeve had this fit for the full length of the stroke the engine would never run. The sleeve has a tapered bore, loose at the bottom and tight for the last 1/4 inch or so at the top. When cold the piston/sleeve does not have the correct running fit. The correct fit/seal is achieved at operating temperature. As the engine warms up the sleeve expands slightly more than the piston and the fit settles in to it's correct seal.

If the engine is turned over when cold the fit will be damaged. During break-in the engine must be run at it's operating temperature and rpm using the fuel that will be used in its future operation, the engine must also have lots of lubrication at this time.

The only way to get the temperature and rpm up with a rich two stroke setting is to use a much smaller propellor than would be used normally.

When I break in a new ABC engine I mount it on a test stand. I heat the head with a heat gun to loosen the fit. I take it up to it's rpm and let it run a 6oz tank out. I shut it off rich. Let it cool down completely. Do this four or five times, it is now ready for use.

I am not the club engine expert.

Ed S
Old 10-17-2003, 05:49 PM
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idranoel
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Default RE: Tweaking TT .40 for max performance?

The method I used is a modification of the method for ABC engines that Dub Jett recommends on the Jett Enginerring site. For a TT .40, this is a rough review of the method. Get an APC 9x6 and chop an inch off both ends. Start the engine (I didn't worry about preheating the engine with a dryer, heat gun, etc.) and lean it out till its running around 20,000 and then back it off a little. Not too much or you won't get the engine nice and hot and, as the gentelman explained above, it has to get hot. Mine ran at about 19,950. I ran about three thanks through it letting it cool down almost completely between runs. I kept the mixture just rich enough to get some healthy smoke and ocassionally leaned it out a few times a tank till it was really screaming (this is when it hit hte 19,950). This seemed to have worked great for me. I have now run about a dozen or so tanks through it and it is a picture of reliability. Consistently right around 16,000 and I'm not pushing it to the limit.

For the Jett Q500 engines, Dub says to lean it out till it hits like 27,000. WOW!
Old 10-21-2003, 10:30 PM
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rsieminski
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Default RE: Tweaking TT .40 for max performance?

What will this method accomplish? 19K for a new engine sounds kinda high for the bushed con rod?

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